Apoptosis, or programmed cell death, is a physiologic process essential to the normal development and homeostasis of multicellular organisms. Derangements of apoptosis contribute to the pathogenesis of several human diseases including cancer, neurodegenerative disorders, and acquired immune deficiency syndrome.
The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily of cytokines, is a type 2 membrane protein that is expressed in the majority of normal tissues and can undergo protease cleavage, resulting in a soluble form able to bind to TRAIL receptors, (Wiley S R. et al., Immunity. 1995; 3:673-682; Daniel P T et al., J Immunol. 1994; 152:5624).
Ligands of this family generally recognize and bind to a limited subset of cognate receptors on the cell surface, leading to signal transduction cascades downstream of the receptor, allowing the activation of a large panel of signalling pathways including NF-kB or caspase activation. TRAIL induces apoptosis of certain transformed cells, including a number of different types of cancer cells as well as virally infected cells, while not inducing apoptosis of a number of normal cell types and is thus of particular interest in the development of cancer therapies, (Walczak et al., Nature Medecine. 1999; 5/157-163, Ashkenazi A. et al., J Clin Invest. 1999; 104:155).
There are four known cell surface receptors for TRAIL. TRAIL Receptor 1 (TRAIL-R1, DR4) and Trail Receptor 2 (TRAIL-R2, DR5, Apo-2, TRICK2, Killer, TR6, Tango-63) have a cytoplasmic death domain and are able to trigger apoptosis in tumor cells via downstream caspase activation. The other two receptors, TRAIL Receptor 3 (TRAIL-R3, DcR1, TR5, TRIDD, LIT) and TRAIL Receptor 4 (TRAIL-R4, DcR2, TRUNDD) lack a cytoplasmic death domain and do not mediate apoptosis. In addition, osteoprotegerin (OPG), a soluble (secreted) member of the TNF receptor family of proteins, also binds TRAIL.
The intracytoplasmic domains of DR4 and DR5 each include a so-called death domain. After activation of the receptors DR4 and DR5, the fas-associated death domain adapter molecule is recruited to the receptor, leading to an autoproteolytic cleavage and activation of initiator caspase-8. DR4 and DR5 have been reported to transduce an apoptotic signal to TRAIL sensitive cancer cells, upon binding of TRAIL. Active caspase-8 in turn triggers the proteolytic activation of downstream caspases including caspase-3. Downstream caspases ultimately degrade a broad range of cellular proteins, and apoptosis is finalized.
Expression of either DR4 or DR5 is frequently detected in human cancers, including colon, gastric, pancreatic, ovarian, breast, and non-small-cell lung cancer with low or no expression in normal tissues.
In the development or progression of many diseases it is often the case that cells are not deleted. In many autoimmune diseases and inflammatory conditions, the surviving activated cells attack normal tissues or cells. Further, progression of tumorigenesis and the proliferative pannus formation of rheumatoid arthritis are characterized by the unchecked proliferation of cells. Thus insufficient apoptosis leads to the development of disease, and the uses of apoptosis-inducing ligand or agonistic MAb to enhance apoptosis are considered as a potential therapeutic strategy for eliminating those unwanted cells
TRAIL induces apoptosis in a wide range of haematopoietic and solid tumor cells, while sparing most normal cells. TRAIL has strong apoptosis-inducing activity against cancer cells in vitro and potent antitumor activity against tumor xenografts of various cancers in vivo.
TRAIL and its derivatives, including agonistic antibodies targeting TRAIL receptors are attractive compounds for cancer therapy due to their ability to induce tumor regression without significant side effects.
There are many instances in the patent literature of efforts to use polypeptides derived from the TRAIL ligand as a therapy against cancerous cells (US20090131317; U.S. Pat. Nos. 6,469,144; 6,740,739; US20070026000; U.S. Pat. No. 6,444,640; US20050244857; US20050233958; U.S. Pat. No. 7,736,637).
TRAIL polypeptides have been used to induce the TRAIL apoptotic pathway, but they have the drawback of a short half-life.
Currently, a great deal of attention has focused on the development of novel immunotherapy strategies for the treatment of cancer. One such strategy is antibody-based cancer therapy.
The most prominent determinant of the above targeting properties is the size of the antibody-based molecule relative the degree of specificity, the retention in tumors and their clearance. Another important feature of antibody-based molecules is valence, as significantly greater tumor retention has been associated with multivalent binding to target, (Adams et al., Cancer Res. 1993; 51:6363-6371; Wolf et al., Cancer Res. 1993; 53:2560-2565).
As mentioned earlier, agonistic antibodies against DR4 or DR5 have been produced and represent a new generation of cancer therapy. Works have been conducted also on the use of agonistic antibodies directed against the TRAIL receptors in order to induce the TRAIL apoptotic pathway.
Agonistic monoclonal antibodies that specifically bind to DR4 or DR5 are supposed to be able to directly induce apoptosis of targeted tumor cells, (Buchsbaum D J et al., Future Oncol. 2006; 2:493; Rowinsky E K et al., J Clin OncoL 2005; 23:9394).
Other patents relate to the use of agonistic antibodies directed against DR4 or DR5, or DR4 and DR5, or to the combined use of antibodies against DR5 and another chemotherapeutic agent: US20040147725; US 20090022707; US20080248037; US20020155109; U.S. Pat. Nos. 6,461,823; 6,872,568; 7,064,189; 6,521,228; 704,502.
Combined treatment with agonistic antibodies directed against different TRAIL receptors, for example DR4 and DR5, have been developed as well. Agonistic bispecific antibodies that bind DR4 or DR5 (or hybridomas producing such agonistic MAbs) may be employed as starting materials in various procedures (WO 2002/0155109).
These include anti-DR5 MAb lexatumumab, (Plummer R. et al., Clin Cancer Res. 2007; 13:6187), the anti-DR5 MAb apomab, (Adams C. et al., Cell Death Differ. 2008; 15:751), the anti-DR5 MAb LBy135, (Li J. et al., AACR Meeting Abstracts. 2007. Abstract 4874), the anti-DR5 MAb WD-1, (Wang J. et al., Cell Mol Immunol. 2008; 5:55) and the anti-DR5 MAb AMG655, (Wall J. et al., AACR Meeting Abstracts. 2008. Abstract 1326, Kaplan-Lefko P. et al., AACR Meeting Abstracts. 2008. Abstract 399). A consistent finding from all these studies is the considerable variability in the sensitivity of various tumor cell lines to anti-DR5-mediated cytotoxicity.
Anti-DR4 or anti-DR5 agonistic antibodies, including mapatumumab or lexatumumab respectively are also well tolerated in patients (Herbst R. S. et al., J Clin Oncol. 2006; 24(18S)/3013; Hotte S. J. et al., Clin Cancer Res. 2008; 14/3450-3455; Wakelee H. A et al., Ann Oncol. 2010; 21/376-381; Fox N. L. et al., Expert Opin Biol Ther. 2010; 10/1-18).
Lexatumumab (also known as ETR2-ST01) is an agonistic human monoclonal antibody against DR5 used in the treatment of cancer. HGS-ETR2 antibodies were generated by HGS through collaboration with Cambridge Antibody Technology.
Tigatuzumab (CS-1008) is a humanized IgG1 monoclonal antibody composed of the CDR regions of mTRA-8. The murine anti-DR5 monoclonal antibody, TRA-8 (mTRA-8), was selected from a series of anti-DR5 monoclonal antibodies based on its specificity, ability to trigger apoptosis in vitro without the use of crosslinking reagents, and lack of toxicity to human hepatocytes, (Buchsbaum D J et al., Clin Cancer Res. 2003; 9:3731; Ichikawa K. et al., Nat Med. 2001; 7:954).
Tigatuzumab mediates a very similar pattern of in vitro cytotoxicity and in vivo antitumor efficacy as mTRA-8. It was shown to have potent in vitro cytotoxicity to a variety of human tumor cell lines and in vivo antitumor efficacy in murine xenograft models of human cancers. Its in vitro cytotoxicity and in vivo antitumor efficacy can be substantially enhanced in combination with a variety of chemotherapeutic agents and/or radiation, (Buchsbaum D J et al., Clin Cancer Res. 2003; 9:3731; DeRosier L C et al., Clin Cancer Res. 2007; 13:5535s).
Anti-DR4 and anti-DR5 antibodies have been tested in associations, together or with other chemotherapeutic agents or therapies. A combined treatment of colorectal tumors with two agonistic antibodies HGS-ETR1 (anti-DR4) and HGS-ETR2 (anti-DR5) and radiotherapy let to enhanced effects in vitro and dose-dependent growth delay in vivo (Marini P et al., Oncogene. 2006; 25 (37):5145-54). Fully human agonistic antibodies to DR4 and DR5 demonstrated in primary and cultured lymphoma cells induction of apoptosis and enhancement of doxorubicin- and bortezomib-induced cell death (Georgakis G V et al., Oncogene. 2006; 25(37):5145-54).
It has been found that the expression of DR5 and susceptibility to TRAIL-induced apoptosis of breast cancer cells is enhanced by the radiation, suggesting that combined with radiation, the efficiency of TRAIL would be increased in cancer therapy (Chinnaiyan A. M et al., PNAS. 2000; 97/1754-1759).
The combination of antibody and chemotherapy usually enhances the degree of apoptosis and can partially reverse resistance in some cell lines (Buchsbaum D J et al., J Clin Cancer Res. 2003; 9:3731; DeRosier L C et al., Clin Cancer Res. 2007; 13:5535s; Oliver P G et al., Clin Cancer Res. 2008; 14:2180; Derosier L C et al., Mol Cancer Ther. 2007; 6:3198; Long J W. et al., J Surg Res. 2007; 137:167).